At the foundation of virtually all airborne, space-based and ground-based Earth observations is the TRF, or Terrestrial Reference Frame. The TRF relies on an accurate calculation of the geocenter of the Earth (the center mass of the Earth). However, one complication is that the geocenter is constantly changing with respect to the Earth’s surface. By using a network of ground stations equipped with telescopes and lasers that fire pulses at specific satellites, scientists can calculate where the geocenter of the Earth is at any given time to a few millimeters to ensure our Earth observations are accurate.